Cameras and camcorders with an autofocus function have been known. In these imaging apparatuses, focusing is generally performed by moving the whole or a part of a lens system of an imaging lens using a drive systems such as a motor or the like. On the other hand, in recent years, a number of small-size information terminal apparatuses, such as a cellular phone, a personal digital assistant (PDA), and the like, which includes an imaging module to have an imaging function, are becoming available on the market. Imaging optical systems in these information terminal apparatuses often employ pan focus, in which the depth of field of a lens is utilized, as a focusing method in favor of ease of miniaturization and configuration.
Recently, a fluid lens system in which the focal length can be changed without moving parts has been developed (Philips Research Press Release, “Philips' Fluid Lenses Bring Things into Focus”, Mar. 3, 2004, on the Internet <URL: http://www.researchphilips.com/newscenter/archive/2004/fulidfocus.html>). This system is composed of two immiscible fluids (lens materials) of different refractive indices, which are loaded in a cylindrical tube and whose shapes are electrically controlled.
As described above, in recent years, it is often that small-size information terminal apparatuses have an imaging function and employs pan focus as a focusing method. However, in such apparatuses, a demand for image quality is growing year after year. Also, a demand is being shifted from the pan focus optical system to an autofocus optical system. However, autofocus in the related art is performed by moving an imaging lens using a drive system such as a motor or the like. Therefore, a lens moving mechanism is required, which is disadvantageous in terms of ease of miniaturization and configuration.